I use ISO 400 when I’m doing interviews and have my own lighting. You could use ISO200, but with 400 you have to close down a couple of stops on the iris and that will give a little bit deeper depth of field. A 6″ DOF looks pretty for products and flowers, but is not very practical for an interview.
When you are outside use ISO200 and dial in the Neutral Density filters (2,3,4) as needed.
It’s a great camera, have fun!
Joe